<?php

/**
 * Processes an entire attribute array for corrections needing multiple values.
 * 
 * Occasionally, a certain attribute will need to be removed and popped onto
 * another value.  Instead of creating a complex return syntax for
 * HTMLPurifier_AttrDef, we just pass the whole attribute array to a
 * specialized object and have that do the special work.  That is the
 * family of HTMLPurifier_AttrTransform.
 * 
 * An attribute transformation can be assigned to run before or after
 * HTMLPurifier_AttrDef validation.  See HTMLPurifier_HTMLDefinition for
 * more details.
 */

class HTMLPurifier_AttrTransform
{
	
	/**
	 * Abstract: makes changes to the attributes dependent on multiple values.
	 * 
	 * @param $attr Assoc array of attributes, usually from
	 *			  HTMLPurifier_Token_Tag::$attr
	 * @param $config Mandatory HTMLPurifier_Config object.
	 * @param $context Mandatory HTMLPurifier_Context object
	 * @returns Processed attribute array.
	 */
	function transform($attr, $config, &$context) {
		trigger_error('Cannot call abstract function', E_USER_ERROR);
	}
	
	/**
	 * Prepends CSS properties to the style attribute, creating the
	 * attribute if it doesn't exist.
	 * @param $attr Attribute array to process (passed by reference)
	 * @param $css CSS to prepend
	 */
	function prependCSS(&$attr, $css) {
		$attr['style'] = isset($attr['style']) ? $attr['style'] : '';
		$attr['style'] = $css . $attr['style'];
	}
	
	/**
	 * Retrieves and removes an attribute
	 * @param $attr Attribute array to process (passed by reference)
	 * @param $key Key of attribute to confiscate
	 */
	function confiscateAttr(&$attr, $key) {
		if (!isset($attr[$key])) return null;
		$value = $attr[$key];
		unset($attr[$key]);
		return $value;
	}
	
}

